Can network sharing problems be understood?

Can network sharing problems be understood?

I'm trying to diagnose occasional network sharing problems between my two home Windows 7 PC's. I realize that there are lots and lots of problems on Google like this. Usually, the advice seems to consist of "try this" or "try that." Is there any way of actually understanding what's going on? For example, I usually turn off my two home Windows 7 PC's overnight. Each PC contains folders that are shared with "everyone". The following situation occurred when I brought these PC's up this morning:

a. After I turned on PC1 first and turned on PC2 later, then PC1 could see the shared folders on PC2, but PC2 could not see the shared folders on PC1.

b. Then I turned both PC's off, then turned on PC2 first and turned on PC1 later. After that procedure, both PC's could see the shared folders on the other PC.

While I'm not sure if this is consistent behavior, is there any way to actually understand what's happening here? For example, is there an internal table within Windows 7 that lists shared folders on other PC's? If so, how can I view this internal table?

I note that nbtstat -a lists the local PC but not the other one, so I assume that this is NOT the correct table.

Thanks for any suggestions, simple tutorials, internal table descriptions, or other ways to understand what's happening.

Are you using a Home Group? I've found the best, IMHO, way to network is NOT to use a home group but to setup each machine with accounts that exactly match (userid & PW) of each machine it will connect to. BTW: the extra accounts can be hidden from the Logon screen. Then setup the Networking to only allow connection to Authenticated Accounts. HTH advsharing.JPG

RG:
I'm using Work Groups, not HOme Groups. I have also found the Home Groups seemed to be less reliable than Work Groups. I'm not sure I understand what you are suggesting: the PC's have different usernames because they are used by different people; are you suggesting that both usernames/PW need to be the same? Or that there needs to be a second account that DOES have the same username/PW but is not used?

Are you also suggesting that the problem I first described is more related to user permissions than to network addressing?

In any event, my original question was whether I could know for sure what was wrong by viewing internal Windows 7 tables, instead of having to guess what was wrong and try things until something worked.

Once in a great while I'll have a computer or two that will not list in Network. However if I enter the network address of the missing computer it will pop right up. If this might be such in your case you might try making a new folder and drag or copy the Network location to it when present. Then go to that folder and click on the shortcut when it doesn't happen to show, if it pops right up or with just a slight delay, it's just some funky discovery glitch. If it really can't be discovered you'll get an error that the location cannot be found instead.

I have about a dozen network computers with maybe 60 shared resources and going through network discovery can be a bit slow so I have a toolbar pointed at a folder of network shortcuts to bypass that whole discovery process.

Say you have 3 users: Larry, Curly, and Moe!
Each machine would have 3 accounts and they would be identical as to User name and PW.
On Larry's machine you, via the registry, can hide the accounts for Curly & Moe from the Logon Screen, instructions below.

Before you begin with the instructions you should back up your System.

1. Start, Run and type regedit and click OK
2. Navigate to HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\Userlis t.
You will not see this folder if you do not have show hidden system files turned on.
3. Create a DWORD value, right click on the User list label file on the left side of the screen and select New>DWORD. You'll see the new entry in the right pane of the window, rename this value the name of the user account you want hidden (exactly how it is listed in the Startup screen, case sensitive) and leave the value at 0.
4. Close your Registry Editor.
5. Restart the PC.

The one thing Windows stumps networking are mainly 2: share*+*security settings.
1. The folder, drive, or file must be set to share.
[Properties-Share tab; only the owner and admin can make changes]
2. The folder, drive, or file, security of which must be set to allow ERWD (execute, read, write, delete), either by 'Everyone', or by specific account username(s).
[Properties-Security tab; only the owner and admin can make modifications]

If 'User' is set to 'Everyone', then no username/password is required. It is equivalent to 'public access-able'.
But how much 'access-ability' is allowed, even to 'Everyone'? It is determined by your setting(s) on ERWD. You may allow a user to execute-only, read-only, etc.

It is equivalent to command prompt CHMOD (drwx; delete, read, write, execute) and the set binary values. They are equivalent to the ERWD in Windows GUI.

There is a 3rd that affects networking, a slightly advanced setting. It is Global Policies (GPedit). For example, if the rule(s) in Gpedit does not allow access to a specific folder/file, or disallow to execute a file, then the security+share settings are overridden and ignored.

Thanks for all of your responses. However, here is a clearer description of the problem, which just occurred this morning:

I brought up both of my home PC's, each of which has a folder shared with the other PC. On PC1, I created a desktop shortcut to the shared folder on PC2. This shortcut worked successfully and displayed the shared folder on the other PC at 7:27 am, 7:31 am, and 7:47 am.

Since I was using shortcuts, there was no chance of a typing error. The shortcut has continued to fail in the same way. The other PC was on the whole time and was not doing anything unusual. What would cause the network path on the first PC to be lost after it successfully worked several times ? Thanks for any further thoughts.

Do you have anything else you can use to verify network connectivity with when that happens? Both from the server and the client; sometimes a network card will work intermittently as it is deteriorating and a second failed network connection let's one quickly zoom in on the problem's location. Latest drivers for each NIC might help especially for Windows 7 if Windows loaded working defaults. There was a bug in 7 where networking would just stop responding and the system had to be rebooted but I haven't run across that in the last couple of years or so. Also the assumption is that when this happens you've gone to the share directly and verified that there are no issues with the partition or drive it resides on.

A possibility of the shared problem: DHCP on the router.
The net address (e.g. 192.168.1.123) is dynamically assigned by the router. If the DHCP/route setup is not properly setup, the net address of the same PC could change whenever the PC, or router, or both, are rebooted (power off-on), or has/have been powered off for a long time. This could explain the 'lost' of the PC in the network.
Diagnose:
When the PC shared folder is available, in a command-prompt, type IPCONFIG on the shared PC *locally* (not doing it on the remote PC). Note the net address (e.g. 192.168.0.8).
When the PC shared folder is unavailable, use IPCONFIG on the local PC to obtain the local PC's net address. If the net address is not the same, it is DHCP setup problem.
Resolution if above is true:
1. Go into router setup. Set the DHCP net address persistent on the problem PC. Persistence: Router's DHCP is to assign the same net address to the same PC every time. (Not all routers have this persistence feature.)
2. Go into router setup. Use a static net address for the PC. Static: A fixed net address, not assigned by DHCP.
(DHCP is to dynamically assign a net address to a PC as soon as it is attached to the local network. No worry of error by manually assigning same static, fixed, net address to 2,3 PCs. Or tediously assign 100s of addresses).

Static address has its place. For small LAN (Local Area Network), it is easier to manage and diagnose. In sharing, the PC is persistent, especially when you map the folder/PC. (Your desktop icon for the shared folder is one method of mapping.)
It is a lot easier to manage and setup if a network device, such as printer, has a static address. You can also use special/custom treatment on a static address device.
General:
Router setup is usually via browser (Internet Explorer, Firefox, Chrome). Router net address is usually 192.168.0.1 or 192.168.1.1. Read the label on the router or its manual for details.

Thanks to F.U.N and Scaisson for your helpful suggestions. However, although intermittent hardware failure is always possible, there is no other evidence of it besides the current problem that I see.
F.U.N.: If a network card were beginning to fail, I would expect that there would be other signs of it, including intermittent problems loading websites or webpages. But there is no other problem that I can detect. All internet access is reasonably fast and accurate. Also, when the shared folders/files are accessible, access is fast and accurate with no problems in file/folder content or organization. I can edit a file on the other PC and the edits are done and saved correctly. I searched the Dell website and found a Network driver that I downloaded and installed but I got the same error on with the shared folder access after I installed it, so I don't think that's the problem.
Scaisson: There is also no other sign of router malfunction. I checked the local PC address with IPCONFIG (actually on both PC's ) and also compared that to the router's DHCP List. All of the Host Names and IP addresses stayed the same both before and after the failure of shared access.

A few other observations:
---when the shared access fails, it does not come back until I reboot. When I DO reboot, the shared access returns ALMOST every time. Once in a while, the shared access doesn't return even after a reboot and I have to reboot again.

---if, after a reboot, the shared access is successful, then it works for a while (average: half an hour) and then fails with no other warning or error indicated.

--sometimes it seems that the shared access stays up longer if the PC's are not being used much. But if we are accessing the internet a lot, then shared access goes down quicker. But I'm not entirely sure about that.

--we have two PC's and both have the same problem. That is, after a reboot on both PC's, each PC can access shared folders on the other PC for a while. But both PC's eventually fail at shared access, but they do NOT fail at the same time.

It's very puzzling to me.

Any other ideas about what the problem might be and/or how to track it down?

When in problem status, can you ping the other PC?
[Command Prompt-Type "ping -a {IP address, e.g. 192.168.1.123}"]
If the ping cannot find the other PC ...
Maybe time to look for intermittent transmission problem.

You did not mention if the LAN is all wireless, all wired, or mixed.
A. If all wireless then there could be one remote possibility that the wireless goes to sleep and won't wake up. (Wireless on the router, or the wireless hardware in your PC; hence reboot would wake them/it up.)

B. In the following, I assume it is all hardwired:
1. Add a switch/hub between your router LAN connector and the PCs. That is, router LAN port is one single cable to the new switch (if it is not auto MDI/MDIX, connect to the 'up-port'). All PCs connect to the new switch.
2. Check if the problem still exists;
Problem gone: The router has a problem
Problem gone: The LAN port on the router has intermittent connection problem. Or the net cable itself. Try move cable to another LAN port on the router. Or use a new net cable.
Same Problem: Router is good. Go to 3.
3. If problem still exists, change all the network cables from the PCs to the new switch. To economize, try 2 network cables on only 2 'problem' PCs first. Then test the 2 PCs network folder accessibility (can simply use ping):
Problem gone: Network cable(s) problem.
4. But Internet access is not consistent and is intermittent:
a. Network cable from the new switch/hub to router is a problem. Or the LAN port on the router is intermittent. Try new cable to different LAN port on the router.
b. Check connectivity/network-cable from router WAN port to cable modem, or check video cable that is screwed to the router video connector. (Verizon router also has video cable connector, RG59 screw-on type.)

The Following User Says Thank You to scaisson For This Useful Post:

Thanks to scaisson and your suggestion to check the PING status. I am hopeful that the problem may be solved !!!!

Both PC's are wireless. I checked the PING times from both PC's to the other one, and found the times from PC1 to PC2 were in the hundreds of milliseconds with an occasional packet being lost. That seemed much too long, since both of these PC's are located less than 20 feet directly above the router, which is in the basement. So I looked at the location of the router in the basement and noticed that a metal furnace duct was close to the router. Furthermore, (I don't why I didn't think of this before) PC1 (but not PC2) sits on a desk consisting of a plywood top sitting on two steel two-drawer file cabinets. I'm guessing that the WiFi signal has to fight its way through the furnace duct and three or four layers of steel to get to PC1. So I moved PC1 to the basement close to the router. Now the PING times on both PC's are less than 2 milliseconds with no packets lost so far. So I am going to leave PC1 in the basement today and see if the shared folder access to the PC is lost. If shared folder access is NOT lost today, then I will conclude that the poor WiFi connection is likely the cause of this problem. Thanks so much !!! I wouldn't have thought of checking the PING times to see if there might be a problem there. I will report back if the problem continues. If not, I believe it is solved. Thanks again !!!

Well, I spoke too soon. After moving both PC's to within 6 feet of the router, the problem returned. Then I turned off wireless access and attached network cables and the problem went away. With wired access, each PC could access the shared folder on the other PC and also the internet and all other network devices. So, as of now, the situation is:
a. Windows Shared folders using wireless access to the router works only intermittently. Ping times between PC's range from 5 ms to 500 ms.
b. Windows Shared folders using wired access to the router works without error. Ping times between PC's are less than 1 ms.
c. All other wireless and wired access seems to work, including accessing the internet and a local wireless printer.

What could cause access to shared folders to fail intermittently only while connected wirelessly to the router?

I am not sure this helps. It is also the hardest to pin point: Intermittent failure.
I would make sure that it is THE problem FIRST before spending $$ on repair.

One thing to check: virus infection or zombied (PC controlled by hacker/spammer). Obviously virus scan. Use process explorer to see if uP usage exceeds 60%. Also check network traffic. A zombied PC may usurp all the network traffic, hence ping and access problem.

Radio (Wifi) transmission is a power device system (not unlike power supply except the power delivered is radio/electromagnetic power).
It needs comparatively high power versus most systems in devices. The transistors (MOSFET) or the IC (Integrated circuit), or the embedded radio system of an IC, get pretty hot, 60C and hotter. Sometimes hot spot exists in the semiconductor junction.

Again, I would not spend money on the fix right away as it is a rare problem.
Maybe your problem is software driver/virus related.

Frequently, rebooting would make it work again. Then after working well for while the radio (Wifi) would die a gain. It is a partial failure due to heat problem, or slow failure from heat problem. Cannot blame the IC or MOSFET all the time though. Sometimes the slow failure of capacitors in its circuit are the culprit. And sometimes it is even the result of power supply slow failure.

We now know your problem is Wifi related, not hard wire.
Borrow a Wifi router and replace the present one.
Same problem? Go after PC's own wireless: One PC on hard wire LAN. The other on Wifi, then vice versa.

As I said, the problem is remote and should test it last. Or, if you're not interested in the root of the problem, replace-until-fixed works too.

[Calling Wifi a radio is a more correct term. Radio is not confined to AM/FM applications. Wifi is just a specialized radio, a subset of radio. ]